add linting to test files, and fix some linting errors

Author: dantownsend

.github/workflows/tests.yaml

@@ -21,9 +21,9 @@ jobs:
                   pip install -r requirements.txt
                   pip install -r tests/test-requirements.txt
             - name: Mypy
-              run: mypy piccolo
+              run: mypy piccolo tests
             - name: Flake8
-              run: flake8 piccolo
+              run: flake8 piccolo tests
 
     postgres:
         runs-on: ubuntu-latest

tests/apps/migrations/auto/test_migration_manager.py

@@ -2,7 +2,7 @@
 from piccolo.columns.column_types import ForeignKey
 from unittest.mock import patch, MagicMock
 
-from asyncpg.exceptions import UniqueViolationError
+from asyncpg.exceptions import UniqueViolationError  # type: ignore
 from piccolo.apps.migrations.auto import MigrationManager
 from piccolo.apps.migrations.commands.base import BaseMigrationManager
 from piccolo.columns import Varchar, Text

tests/sqlite_conf.py

@@ -6,4 +6,3 @@
 
 
 APP_REGISTRY = AppRegistry(apps=["tests.example_app.piccolo_app"])
-

tests/table/test_insert.py

@@ -1,4 +1,3 @@
-from unittest.case import TestCase
 from ..base import DBTestCase
 from ..example_app.tables import Band, Manager